Matching blender dimensions to paper cutout
Tried with a Cube and seems to be working.
But there is one thing that could be good to discuss with developer of this addon on Blenderartists

Cube

Object Dimension set 0.2 m
Object Scale is always better to have a 1 (Apply Scale Ctrl+A)


Addon

press Unfold
or select edges press Mark as Seam and press Unfold

Export (or skip for now)

Model Scale 1
Page Size 1 m


When export window popups go to options (right up gear icon)

it seems addon does not respect export setup from 3Dview
by default addon change scale automatically to fit A4 paper format



change scale to 1
if format is not enough for unfolded object it warns you



change paper format, addon will inform you if it is enough